These studies are targeted to provide the basic scientific information needed to understand the mechanisms whereby age-dependent perturbations in physiological control systems lead to the inability of the organism to maintain homeostasis. The research has impact on the mechanism underlying age-related changes in renal function. The thrust of the work is focused on questions dealing with the biology of membranes, including: (1) molecular organization; (2) catalytic properties; (3) selective vectorial transport; (4) hormonal regulation of function; (5) turnover; and (6) failure to maintain structure and function, leading to cell death.